Method and apparatus for analysis of magnetic characteristics of magnetic device, magnetic head, and magnetic recording and reproducing apparatus

ABSTRACT

A method and apparatus for analysis of magnetic characteristics of a magnetic device used for designing a magnetic head. The magnetic head has recording and reproducing characteristics and a recording and reproducing apparatus of magnetic characteristics. The apparatus for analysis of magnetic characteristics includes a data input part, a coupled analysis part, and a result output part. The data input part is provided with data related to the characteristics of substances composing the magnetic device, data related to the magnetic device divided into a plurality of parts, data concerning the boundary conditions for analysis of the magnetic device, and data concerning the boundary conditions for analysis of the magnetic field. In the analysis part, a stress distribution for each of the plurality of parts divided on the basis of the data related to the boundary conditions input from the data input part is obtained, and magnetic characteristics for each of the plurality of parts based on the data concerning the boundary conditions of the magnetic field and the stress distribution of the magnetic device are obtained, and magnetic characteristics of the whole magnetic device are obtained based on the magnetic characteristics of each of the plurality of parts.

This application is a division of U.S. application Ser. No. 08/390,782filed Feb. 17, 1995, now U.S. Pat. No. 5,602,473.

FIELD OF THE INVENTION

This invention relates to a magnetic recording equipment used for anaudio equipment, a video equipment, an information equipment etc., orrelates to a magnetic device such as a transformer and a coil. Thisinvention further relates to a method and an apparatus for analysis ofmagnetic characteristics, a magnetic head, and a recording apparatus forthe aforementioned equipments and devices.

BACKGROUND OF THE INVENTION

As far as a video tape recorder (VTR) and a Digital Audio Tape (DAT) areconcerned, a bulk type magnetic head 38 in FIG. 5 (a), a metal-in-gaptype magnetic head 39 in FIG. 5 (b), and a laminate type magnetic head40 in FIG. 5 (c) etc. are used. The bulk type magnetic head 38 shown inFIG. 5 (a) comprises at least a magnetic substance 42 such as ferrite,sendust, and permalloy which forms a magnetic path, a magnetic gap 41,and a non magnetic material 43 such as glass for fixing two cores ofmagnetic circuits 47, 48 which form the magnetic gap. The metal-in-gaptype magnetic head 39 shown in FIG. 5 (b) comprises at least a highmagnetic saturation substance 44 such as a metal film which forms amagnetic path in the vicinity of a magnetic gap, a magnetic substance 42such as ferrite, sendust, permalloy etc. which forms the magnetic pathbesides the vicinity of the gap, a magnetic gap 41, and a non magneticmaterial 43. The laminate type magnetic head 40 shown in FIG. 5 (c)comprises at least a magnetic substance 45 forming a magnetic path, amagnetic gap 41, and a non magnetic material 46 such as ceramics forsupporting the magnetic substance.

Conventionally, with regard to the bulk type magnetic head 38 and thelaminate type magnetic head 40, a magnetic path was composed ofmagnetically equal materials (magnetic substances 42, 45) and initialpermeability was also considered as being isotropic and equal. In caseof the metal-in-gap type magnetic head 39, although the high magneticsaturation substance 44 such as a metal film which forms the gap partand the other part 42 of the magnetic substance have different initialpermeability, each of the initial permeability was also considered asbeing isotropic and constant. However, a single crystal ferrite or amagnetic thin film generally has anisotropy in crystal, so that theinitial permeability also differs according to the azimuth. Therefore,it can be anticipated that magnetic recording characteristics change inaccordance to the azimuth. Furthermore, the non magnetic material 43such as glass etc. is used for bonding two cores 47 and 48, anddepending on the type of this non magnetic material 43, magneticrecording characteristics of the magnetic head 39 differed greatly.Probably, this was due to the fact that the magnetic, characteristics ofthe magnetic material changed by thermal stress caused by the differenceof thermal expansion coefficients between the non magnetic material 43and the magnetic material 44 composing the magnetic path. However, sincethese phenomena are complicated and difficult to analyze, compositesubstances of a magnetic head were selected and the size of the head wasdesigned on the basis of experiences.

A conventional method for analysis of magnetic characteristics will beexplained in an example of a magnetic head as one of a typical magneticdevices.

Now, Maxwell's fundamental equations of electromagnetic field which rulethe electromagnetic field are shown in the following equations 1 to 4(Finite Element Method of Electrical Engineering, Autor: TakayoshiNakada, Publisher: Morikita Shuppan, 1982). ##EQU1## In the above-notedequations, B represents a magnetic flux density, H represents a magneticfield strength, D represents a dielectric flux density, E representsfield strength. J represents a current density, t represents time, and ρrepresents a charge density. A magnetic flux distribution and a magneticfield distribution comprising magnetic characteristics can be obtainedby solving the equations 1 to 4 in combination under appropriateboundary conditions.

In a conventional method of analyzing magnetic characteristics of amagnetic device, the equations 1 to 4 are solved in combination underoptional boundary conditions, for example, with a continuous magneticflux, to obtain a magnetic flux distribution and a magnetic fielddistribution by forming magnetic flux continuously. By referring to amethod of analyzing magnetic characteristics of a magnetic head by usingthe finite element method, a magnetic body comprising a magnetic path isdivided into several elements, and these boundary conditions andmaterial characteristics of each element and initial permeability μ or acurve of magnetic flux density--magnetic field strength (B-H curve) areinput in an apparatus for anaylsis of magnetic characteristics. Theconventional method for analysis of magnetic characteristics wasconducted such that the magnetic characteristics such as the curve ofmagnetic flux density--magnetic field or the initial permeabilitydefined as the equation 5 were measured in advance, and the measureddata were provided at an input part of the apparatus for analysis ofmagnetic characteristics. ##EQU2##

On the other hand, the direction of an easy axis of a magnetic substanceis determined by an angle formed with a magnetic field, and initialpermeability changes depending upon this angle. In other words, whenmagnetic characteristics of a magnetic device are analyzed by usinginitial permeability, even if the initial permeability of each partchange depending on the direction of a magnetic moment in each part ofthe magnetic device, the initial permeability were input in aconventional apparatus for analysis of magnetic records without takingthe direction of the magnetic moment in each part into consideration.

Similarly, a curve of magnetic flux density--magnetic field strengthalso changes the optimum point of energy due to the direction of anexternal magnetic field, and a magnetic flux within a magnetic bodychanges the flowing direction. Therefore, when the flow of magnetic fluxin the entire device is obtained by using the same curve of magneticflux density--magnetic field strength and the equation 3 which shows thecontinuity of magnetic flux, the results obtained do not hold good forthe actual state.

Furthermore, when a single crystal magnetic material or a magnetic thinfilm is used, initial permeability or a curve of magnetic fluxdensity--magnetic field differ greatly according to the azimuth. Inaddition, the initial permeability or the curve of magnetic fluxdensity--magnetic field also changes in accordance to internal stresspossessed by the magnetic device. However, it was impossible to obtainthe initial permeability or the curve of magnetic field--magnetic fluxdensity for each azimuth of respective material or element composing themagnetic device.

Moreover, when a magnetic device is composed of a plurality of magneticsubstances and non magnetic substances, and when each substance hasdifferent thermal and internal stress, it was hardly taken intoconsideration how the magnetic characteristics in each part or in theentire magnetic device changed.

SUMMARY OF THE INVENTION

It is an objective of this invention is to solve the above-mentionedproblems in the conventional methods by providing a method and anapparatus for analysis of magnetic characteristics of a magnetic devicewhich are used for designing excellent magnetic heads. A furtherobjective of this invention is to provide a magnetic head havingexcellent recording and reproducing characteristics. A further objectiveof this invention is to provide an excellent magnetic recording andreproducing apparatus.

In order to accomplish these and other objects and advantages, a methodfor analysis of magnetic characteristics of a magnetic device of thisinvention is conducted by measuring magnetic characteristics of themagnetic device composed of a magnetic material and a non magneticmaterial with the use of an analysis apparatus, and comprises the stepsof inputting data related to characteristics of the substances composingthe magnetic device, data related to structure of the magnetic devicedivided into a plurality of parts, data concerning boundary conditionsfor analysis of the structure of the magnetic device, and dataconcerning boundary conditions for analysis of a magnetic field of themagnetic device into the analysis apparatus, obtaining a stressdistribution for each of the plurality of divided parts on the basis ofthe data related to the boundary conditions, obtaining magneticcharacteristics for each of the plurality of parts based on the dataconcering the boundary conditions of the magnetic field and the stressdistribution of the magnetic device, and obtaining magneticcharacteristics of the whole magnetic device based on the magneticcharacteristics for each of the plurality of parts.

It is preferable that magnetic characteristics of the entire magneticdevice are obtained by solving an equation for obtaining magnetic fluxand direction of magnetic flux for each of the plurality of parts byusing the data related to the boundary conditions for analysis of themagnetic field and the stress distribution of the magnetic device, incombination and simultaneously with an equation for obtaining magneticcharacteristics of the whole magnetic device from the continuousformulas of magnetic flux.

Furthermore, it is preferable that convergence solutions of magneticcharacteristics of the entire magnetic device are obtained by solving anequation for obtaining magnetic flux and direction of magnetic flux foreach of the plurality of parts by using the data related to the boundaryconditions for analysis of the magnetic field and the stressdistribution of the magnetic device, alternately with an equation forobtaining magnetic characteristics of the whole magnetic device from thecontinuous formulas of magnetic flux.

In addition, it is preferable that magnetic characteristics of theentire magnetic device are obtained by solving an equation for obtainingan absolute value of initial permeability and anisotropy of initialpermeability for each of the plurality of parts by using the datarelated to the boundary conditions for analysis of the magnetic fieldand the stress distribution of the magnetic device, in combination andsimultaneously with an equation for obtaining magnetic characteristicsof the whole magnetic device from the continuous formulas of magneticflux.

It is also preferable that convergence solutions of magneticcharacteristics of the whole magnetic device are obtained by solving anequation for obtaining an absolute value of initial permeability andanisotropy of initial permeability for each of the plurality of parts byusing the data related to the boundary conditions for analysis of themagnetic field and the stress distribution of the magnetic device,alternately with an equation for obtaining magnetic characteristics ofthe whole magnetic device from the continuous formulas of magnetic flux.

It is preferable that the magnetic device comprises a magnetic head, andstress imposed on the plurality of parts is at least one force selectedfrom the group consisting of thermal stress caused by the difference ofthermal expansion coefficients in the composite material and pressureadded externally, and the magnetic characteristics comprise at least oneof the magnetic recording characteristics selected from the groupconsisting of strength of magnetic field generated at a magnetic gappart by an excited coil and magnetic strength of a magnetic medium body.

Furthermore, it is preferable that the magnetic device comprises amagnetic head, and stress imposed on the plurality of parts is at leastone force selected from the group consisting of thermal stress caused bythe difference of thermal expansion coefficients in the compositematerial and pressure added externally, and the magnetic characteristicscomprise at least, one of the magnetic recording and reproducingcharacteristics selected from the group consisting of magnetic fluxdensity at a magnetic gap part, electromotive force caused in a coildisposed at the interlinkage with a magnetic circuit, and amount ofmagnetic flux at the interlinkage with the coil.

In addition, it is preferable that an equation for obtaining magneticcharacteristics against a magnetic field for each of the plurality ofparts by using the data related to the boundary conditions for analysisof the magnetic field and the stress distribution of the magnetic devicesolves at least one equation of motion selected from the groupconsisting of a domain wall motion and a magnetization rotation, hasfrequency dependency including a damping-constant, and obtains frequencydependency of the magnetic device.

A second embodiment of this invention is an apparatus for analysis ofmagnetic characteristics of a magnetic device used for measuringmagnetic characteristics of a magnetic device composed of a magneticmaterial and a non magnetic material, and comprises at least a datainput part, in which data related to characteristics of substancescomposing the magnetic device, data related to structure of the magneticdevice divided into a plurality of parts, data concerning boundaryconditions for analysis of the structure, and data concerning boundaryconditions for analysis of a magnetic field of the magnetic device areinput, and an analysis part, in which a stress distribution for each ofthe plurality of parts divided on the basis of the data related to theboundary conditions is obtained, and magnetic characteristics for eachof the plurality of parts; based on the data concering the boundaryconditions and the stress distribution are obtained, and magneticcharacteristics of the whole magnetic device based on the magneticcharacteristics for each of the plurality of parts are obtained.

A third embodiment of this invention is a magnetic head. A firstconfiguration of the magnetic head comprises a form and magneticsubstances selected most suitably by measuring magnetic characteristicsof the magnetic head composed of a magnetic material and a non magneticmaterial with the use of an analysis apparatus, and comprises the stepsof inputting data related to characteristics of the substances composingthe magnetic head, data related to structure of the magnetic headdivided into a plurality of parts, data concerning boundary conditionsfor analysis of the structure of the magnetic head, and data concerningboundary conditions for analysis of a magnetic field of the magnetichead into the analysis apparatus, obtaining at least one stressdistribution selected from the group consisting of thermal stress causedby the difference of thermal expansion coefficients of the compositematerial and pressure added externally, obtaining magneticcharacteristics for each of the plurality of parts based on the dataconcering the boundary conditions for analysis of the magnetic field andthe stress distribution of the magnetic head including at least onestrength selected from the group consisting of strength of magneticfield generated at a magnetic gap part by an excited coil and magneticstrength of a magnetic recording medium, and obtaining magneticrecording characteristics of the whole magnetic head based on themagnetic recording characteristics for each of the plurality of parts.

A second configuration of the magnetic head of this invention has a formand magnetic substances selected most suitably by measuring magneticcharacteristics of the magnetic head composed of a magnetic material anda non magnetic material with the use of an analysis apparatus, andcomprises the steps of inputting data related to characteristics of thesubstances composing the magnetic head, data related to structure of themagnetic head divided into a plurality of parts, data concerningboundary conditions for analysis of the structure of the magnetic head,and data concerning boundary conditions for analysis of a magnetic fieldof the magnetic head into the analysis apparatus, obtaining at least onestress distribution selected from the group consisting of thermal stresscaused by the difference of thermal expansion coefficients of thecomposite material and pressure added externally, obtaining magneticrecording and reproducing characteristics for each of the plurality ofparts based on the data concering the boundary conditions for analysisof the magnetic field and the stress distribution of the magnetic headincluding at least one element selected from the group consisting ofmagnetic flux density at a magnetic gap part, electromotive force causedin a coil disposed at the interlinkage with a magnetic circuit, andamount of magnetic flux at the interlinkage with the coil, and obtainingmagnetic recording characteristics of the whole magnetic head based onthe magnetic recording and reproducing characteristics for each of theplurality of parts.

A fourth embodiment of this invention is a magnetic recording andreproducing apparatus. A first configuration of the magnetic recordingand reproducing apparatus conducts recording and reproducing ofinformation by relatively moving a magnetic head composed of a magneticmaterial and a non magnetic material and a magnetic medium, and has aform and magnetic substances selected most suitably by measuringmagnetic characteristics of the magnetic head with the use of ananalysis apparatus, and comprises the steps of inputting data related tocharacteristics of the substances composing the magnetic head, datarelated to structure of the magnetic head divided into a plurality ofparts, data concerning boundary conditions for analysis of the structureof the magnetic head, and data concerning the boundary conditions foranalysis of a magnetic field of the magnetic head into the analysisapparatus, obtaining at least one stress distribution selected from thegroup consisting of thermal stress caused by the difference of thermalexpansion coefficients of the composite material and pressure addedexternally, obtaining magnetic characteristics for each of the pluralityof parts on the basis of the data concering the boundary conditions foranalysis of the magnetic field and the stress distribution of themagnetic head including at least one strength selected from the groupconsisting of strength of magnetic field generated at a magnetic gappart by an excited coil and magnetic strength of a magnetic recordingmedium, and obtaining magnetic recording characteristics of the wholemagnetic head based on the magnetic recording characteristics for eachof the plurality of parts.

A second configuration of the magnetic recording and reproducingapparatus of this invention conducts recording and reproducing ofinformation by relatively moving a magnetic head composed of a magneticmaterial and a non magnetic material and a magnetic medium, and has aform and magnetic substances selected most suitably by measuringmagnetic characteristics of the magnetic head with the use of ananalysis apparatus, and comprises the steps of inputting data related tocharacteristics of the substances composing the magnetic head, datarelated to structure of the magnetic head divided into a plurality ofparts, data concerning boundary conditions for analysis of the structureof the magnetic head, and data concerning boundary conditions foranalysis of a magnetic field of the magnetic head into the analysisapparatus, obtaining at least one stress distribution selected from thegroup consisting of thermal stress caused by the difference of thermalexpansion coefficients of the composite material and pressure addedexternally, obtaining magnetic characteristics for each of the pluralityof parts on the basis of the data concering the boundary conditions foranalysis of the magnetic field and the stress distribution of themagnetic head including at least one element selected from the groupconsisting of magnetic flux density at a magnetic gap part,electromotive force caused in a coil disposed at the interlinkage with amagnetic circuit, and amount of magnetic flux at the interlinkage withthe coil, and obtaining magnetic recording characteristics of the wholemagnetic head based on the magnetic recording and reproducingcharacteristics for each of the plurality of parts.

A third configuration of the magnetic head of this invention comprises aring type magnetic head for sending and receiving signals with amagnetic medium, wherein a curve of magnetic flux density--magneticfield strength at rubbing direction differs from a curve of magneticflux density--magnetic field strength at gap depth direction of themagnetic medium of substances comprising a magnetic circuit, and eachsubstance has a higher curve of magnetic flux density--magnetic fieldstrength than in the time of no stress.

A fourth configuration of the magnetic head of this invention comprisesa ring type magnetic head for sending and receiving signals with amagnetic medium, wherein a material having a different thermal expansioncoefficient from that of a material composing the head is bonded on theside of the head.

It is preferable that the material composing the head includes at leastferrite, and the ferrite has a negative magnetostriction constant, and amaterial having a smaller thermal expansion coefficient than that of theferrite is bonded at a part where a magnetic path on the side of thehead is formed at gap depth direction.

Furthermore, it is preferable that the material bonded at a part where amagnetic path on the side of the head is formed at gap depth directioncomprises glass having a smaller thermal expansion coefficient than thatof the ferrite.

In addition, it is preferable that the material composing the headincludes at least ferrite, and the ferrite has a positivemagnetostriction constant, and a material having a larger thermalexpansion coefficient than that of the ferrite is bonded at a part wherea magnetic path on the side of the head is formed at gap depthdirection.

A third configuration of the magnetic recording and reproducingapparatus of this invention conducts recording and reproducing ofinformation by relatively moving a ring type magnetic head and amagnetic medium, wherein a material having a different thermal expansioncoefficient from that of a material composing the head is bonded on theside of the head.

A fifth configuration of the magnetic head of this invention comprises aring type magnetic head for sending and receiving signals with amagnetic medium, wherein initial permeability μ₁ at rubbing directionand initial permeability μ₂ at gap depth direction of the magneticmedium of substances comprising a magnetic circuit meet the followingequation 17: ##EQU3##

A sixth configuration of the magnetic head of this invention comprises aring type magnetic head for sending and receiving signals with amagnetic medium, wherein at least ferrite is used at one part of acomposite material comprising a magnetic circuit of the magnetic head,and initial permeability μ₃ at rubbing direction and initialpermeability μ₄ at gap depth direction of the magnetic medium of theferrite meet the following equation 18: ##EQU4##

A seventh configuration of the magnetic head of this invention comprisesa ring type magnetic head for sending and receiving signals with amagnetic medium, wherein at least a material composing the head is abonded ferrite of a single crystal ferrite and a polycrystal ferrite,and a rubbing side of the magnetic medium has initial permeability μ₅ atrubbing direction of the magnetic medium with the single crystalferrite, and the part which does not rub with the magnetic medium hasinitial permeability μ₆ magnetically isotropic with the polycrystalferrite, and permeabilities μ₅ and μ₆ meet the following equation 19:##EQU5##

According to the method for analysis of magnetic characteristics of amagnetic device of this invention, the method is conducted by measuringmagnetic characteristics of the magnetic device composed of a magneticmaterial and a non magnetic material with the use of an analysisapparatus, and comprises the steps of inputting data related tocharacteristics of the substances composing the magnetic device, datarelated to structure of the magnetic device divided into a plurality ofparts, data concerning boundary conditions for analysis of the structureof the magnetic device, and data concerning boundary conditions foranalysis of a magnetic field of the magnetic: device into the analysisapparatus, obtaining a stress distribution for each of the plurality ofdivided parts based on the data related to the boundary conditions,obtaining magnetic characteristics for each of the plurality of parts onthe basis of the data concering the boundary conditions of the magneticfield and the stress distribution of the magnetic device, and obtainingmagnetic characteristics of the whole magnetic device based on themagnetic characteristics for each of the plurality of parts. As aresult, it is possible to obtain magnetic characteristics accurately inaccordance to the realities, even if magnetic characteristics change ina complicated way due to stress generated within a magnetic device.

It is preferable that magnetic characteristics of the entire magneticdevice are obtained by solving an equation for obtaining magnetic fluxand direction of magnetic flux for each of the plurality of parts byusing the data related to the boundary conditions for analysis of themagnetic field and the stress distribution of the magnetic device, incombination and simultaneously with an equation for obtaining magneticcharacteristics of the whole magnetic device from the continuousformulas of magnetic flux. Accordingly, instability of solutions causedby having a non-linear part or divergence of solutions can be avoided,so that convergence solutions can be obtained stably.

Furthermore, it is preferable that convergence solutions of magneticcharacteristics of the entire magnetic device are obtained by solving anequation for obtaining magnetic flux and direction of magnetic flux foreach of the plurality of parts by using the data related to the boundaryconditions for analysis of the magnetic field and the stressdistribution of the magnetic device, alternately with an equation forobtaining magnetic characteristics of the whole magnetic device from thecontinuous formulas of magnetic flux. Thus, a scale of the matrix can bereduced and present calculators can be used effectively, so that it ispossible to calculate in a practical time.

In addition, it is preferable that magnetic characteristics of theentire magnetic device are obtained by solving an equation for obtainingan absolute value of initial permeability and anisotropy of initialpermeability for each of the plurality of parts by using the datarelated to the boundary conditions for analysis of the magnetic fieldand the stress distribution of the magnetic device, in combination andsimultaneously with an equation for obtaining magnetic characteristicsof the whole magnetic device from the continuous formulas of magneticflux. Accordingly, instability of solutions caused by having anon-linear part or divergence of solutions can be avoided, so thatconvergence solutions can be obtained stably.

It is also preferable that convergence solutions of magneticcharacteristics of the whole magnetic device are obtained by solving anequation for obtaining an absolute value of initial permeability andanisotropy of initial permeability for each of the plurality of parts byusing the data related to the boundary conditions for analysis of themagnetic field and the stress distribution of the magnetic device,alternately with an equation for obtaining magnetic characteristics ofthe whole magnetic device from the continuous formulas of magnetic flux.Thus, a scale of the matrix can be reduced and present calculators canbe used effectively, so that it is possible to calculate in a practicaltime.

It is preferable that the magnetic device comprises a magnetic head, andstress imposed on the plurality of parts is at least one force selectedfrom the group consisting of thermal stress caused by the difference ofthermal expansion coefficients in the composite material and pressureadded externally, and the magnetic characteristics comprise at least oneof the magnetic recording characteristics selected from the groupconsisting of strength of magnetic field generated at a magnetic gappart by an excited coil and magnetic strength of a magnetic medium body.As a result, structure, material, and manufacturing process of amagnetic head composed of various substances can be highly optimized,thereby obtaining a magnetic head having improved recordingcharacteristics than a conventional one.

Furthermore, it is preferable that the magnetic device comprises amagnetic head, and stress imposed on the plurality of parts is at leastone force selected from the group consisting of thermal stress caused bythe difference of thermal expansion coefficients in the compositematerial and pressure added externally, and the magnetic characteristicscomprise at least one of the magnetic recording and reproducingcharacteristics selected from the group consisting of magnetic fluxdensity at a magnetic gap part, electromotive force caused in a coildisposed at the interlinkage with a magnetic circuit, and amount ofmagnetic flux at the interlinkage with the coil. Accordingly, structure,material, and manufacturing process of a magnetic head composed ofvarious substances can be highly optimized, thereby obtaining a magnetichead having improved reproducing characteristics than a conventionalone.

In addition, it is preferable that an equation for obtaining magneticcharacteristics against a magnetic field for each of the plurality ofparts by using the data related to the boundary conditions for analysisof the magnetic field and the stress distribution of the magnetic devicesolves at least one equation of motion selected from the groupconsisting of a domain wall motion and a magnetization rotation, hasfrequency dependency including a damping-constant, and obtains frequencydependency of the magnetic device. As a result, structure, material, andmanufacturing process of a magnetic head composed of various substancescan be highly optimized, thereby obtaining a magnetic head havingexcellent recording and reproducing characteristics up to highfrequencies than a conventional one.

According to the second embodiment of this invention, the apparatus foranalysis of magnetic characteristics of a magnetic device used formeasuring magnetic characteristics of a magnetic device composed of amagnetic material and a non magnetic material comprises at least a datainput part, in which data related to characteristics of the substancescomposing the magnetic device, data related to structure of the magneticdevice divided into a plurality of parts, data concerning boundaryconditions for analysis of the structure, and data concerning boundaryconditions for analysis of a magnetic field of the magnetic device areinput, and an analysis part, in which a stress distribution for each ofthe plurality of parts divided on the basis of the data related to theboundary conditions is obtained, and magnetic characteristics for eachof the plurality of parts based on the data concering the boundaryconditions and the stress distribution are obtained, and magneticcharacteristics of the whole magnetic device based on the magneticcharacteristics for each of the plurality of parts are obtained. As aresult, it is possible to obtain magnetic characteristics accurately inaccordance to the realities, even if magnetic characteristics change ina complicated way due to stress generated within a magnetic device.

According to the first configuration of the magnetic head of thisinvention, the magnetic head has a form and magnetic substances selectedmost suitably by measuring magnetic characteristics of the magnetic headcomposed of a magnetic material and a non magnetic material with the useof an analysis apparatus, and comprises the steps of inputting datarelated to characteristics of substances composing the magnetic head,data related to structure of the magnetic head divided into a pluralityof parts, data concerning boundary conditions for analysis of thestructure of the magnetic head, and data concerning boundary conditionsfor analysis of a magnetic field, of the magnetic head into the analysisapparatus, obtaining at least one stress distribution selected from thegroup consisting of thermal stress caused by the difference of thermalexpansion coefficients of the composite material and pressure addedexternally, obtaining magnetic characteristics for each of the pluralityof parts based on the data concering the boundary conditions foranalysis of the magnetic field and the stress distribution of themagnetic head including at least one strength selected from the groupconsisting of strength of magnetic field generated at a magnetic gappart by an excited coil and magnetic strength of a magnetic recordingmedium, and obtaining magnetic, recording characteristics of the wholemagnetic head based on the magnetic recording characteristics for eachof the plurality of parts. As a result, a magnetic head having excellentreproducing efficiency can be obtained.

According to the second configuration of the magnetic head of thisinvention, the magnetic head has a form and magnetic substances selectedmost suitably by measuring magnetic characteristics of the magnetic headcomposed of a magnetic material and a non magnetic material with the useof an analysis apparatus, and comprises the steps of inputting datarelated to characteristics of the substances composing the magnetichead, data related to structure of the magnetic head divided into aplurality of parts, data concerning boundary conditions for analysis ofthe structure of the magnetic head, and data concerning boundaryconditions for analysis of a magnetic field of the magnetic head intothe analysis apparatus, obtaining at least one stress distributionselected from the group consisting of thermal stress caused by thedifference of thermal expansion coefficients of the composite materialand pressure added externally, obtaining magnetic recording andreproducing characteristics for each of the plurality of parts based onthe data concering the boundary conditions for analysis of the magneticfield and the stress distribution of the magnetic head including atleast one element selected from the group consisting of magnetic fluxdensity at a magnetic gap part, electromotive force caused in a coildisposed at the interlinkage with a magnetic circuit, and amount ofmagnetic flux at the interlinkage with the coil, and obtaining magneticrecording characteristics of the whole magnetic head based on themagnetic recording and reproducing characteristics for each of theplurality of parts. As a result, a magnetic head having excellentreproducing efficiency can be obtained.

According to the first configuration of the magnetic recording andreproducing apparatus of this invention, the magnetic recording andreproducing apparatus conducts recording and reproducing of informationby relatively moving a magnetic head composed of a magnetic material anda non magnetic material and a magnetic medium, and has a form andmagnetic substances selected most suitably by measuring magneticcharacteristics of the magnetic head with the use of an analysisapparatus, and comprises the steps of inputting data related tocharacteristics of substances composing the magnetic head, data relatedto structure of the magnetic head divided into a plurality of parts,data concerning boundary conditions for analysis of the structure of themagnetic head, and data concerning boundary conditions for analysis of amagnetic field of the magnetic head into the analysis apparatus,obtaining at least one stress distribution selected from the groupconsisting of thermal stress caused by the difference of thermalexpansion coefficients of the composite material and pressure addedexternally, obtaining magnetic characteristics for each of the pluralityof parts on the basis of the data concering the boundary conditions foranalysis of the magnetic field and the stress distribution of themagnetic head including at least one strength selected from the groupconsisting of strength of magnetic field generated at a magnetic gappart by an excited coil and magnetic strength of a magnetic recordingmedium, and obtaining magnetic recording characteristics of the wholemagnetic head based on the magnetic recording characteristics for eachof the plurality of parts. As a result, a magnetic head having excellentreproducing efficiency can be obtained.

According to the second configuration of the magnetic recording andreproducing apparatus of this invention, the magnetic recording andreproducing apparatus conducts recording and reproducing of informationby relatively moving a magnetic head composed of a magnetic material anda non magnetic material and a magnetic medium, and has a form andmagnetic substances selected most suitably by measuring magneticcharacteristics of the magnetic head with the use of an analysisapparatus, and comprises the steps of inputting data related tocharacteristics of substances composing the magnetic head, data relatedto structure of the magnetic head divided into a plurality of parts,data concerning boundary conditions for analysis of the structure of themagnetic head, and data concerning boundary conditions for analysis of amagnetic field of the magnetic head into the analysis apparatus,obtaining at least one stress distribution selected from the groupconsisting of thermal stress caused by the difference of thermalexpansion coefficients of the composite material and pressure addedexternally, obtaining magnetic characteristics for each of the pluralityof parts on the basis of the data concering the boundary conditions foranalysis of the magnetic field and the stress distribution of themagnetic head including at least one element selected from the groupconsisting of magnetic flux density at a magnetic gap part,electromotive force caused in a coil disposed at the interlinkage with amagnetic circuit, and amount of magnetic flux at the interlinkage withthe coil, and obtaining magnetic recording characteristics of the wholemagnetic head based on the magnetic recording and reproducingcharacteristics for each of the plurality of parts. As a result, amagnetic head having excellent reproducing efficiency can be obtained.

According to the third configuration of the magnetic head of thisinvention, the magnetic head comprises a ring type magnetic head forsending and receiving signals with a magnetic medium, wherein a curve ofmagnetic flux density--magnetic field strength at rubbing directiondiffers from a curve of magnetic flux density--magnetic field strengthat gap depth direction of the magnetic medium of substances comprising amagnetic circuit, and each substance has a higher curve of magnetic fluxdensity--magnetic field strength than in the time of no stress. Thus, amagnetic head having higher recording and reproducing characteristicsthan that in the time of no stress can be obtained.

According to the fourth configuration of the magnetic head of thisinvention, the magnetic head comprises a ring type magnetic head forsending and receiving signals with a magnetic medium, wherein a materialhaving a different thermal expansion coefficient from that of a materialcomposing the head is bonded on the side of the head. In this way,stress is imposed on the material composing the head, and initialpermeability of the material composing the head can be enhanced, so thatit is effective for enhancing magnetic recording efficiency. It ispreferable that the material composing the head includes at leastferrite, and the ferrite has a negative magnetostriction constant, and amaterial having a smaller thermal expansion coefficient than that of theferrite is bonded at a part where a magnetic path on the side of thehead is formed at gap depth direction. Thus, by imposing tensile stresson the ferrite, initial permeability of the side of the head at gapdepth direction can be enhanced than that in the time of no stress. Inaddition, it is preferable that the material composing the head includesat least ferrite, and the ferrite has a positive magnetostrictionconstant, and a material having a larger thermal expansion coefficientthan that of the ferrite is bonded at a part where a magnetic path onthe side of the head is formed at gap depth direction. Similarly, byimposing tensile stress on the ferrite, initial permeability of the sideof the head at gap depth direction can be enhanced than that in the timeof no stress.

According to the third configuration of the magnetic recording andreproducing apparatus of this invention, the magnetic recording andreproducing apparatus conducts recording and reproducing of informationby relatively moving a ring type magnetic head and a magnetic medium,wherein a material having a different thermal expansion coefficient fromthat of a material composing the head is bonded on the side of the head.As a result, it is possible to obtain a magnetic head having excellentrecording and reproducing characteristics, wherein higher initialpermeability of the side of the head at gap depth direction can beattained than that in the time of no stress, and a magnetic recordingand reproducing apparatus having excellent recording and reproducingcharacteristics than that of a conventional one can be attained.

According to the fifth configuration of the magnetic head of thisinvention, the magnetic head comprises a ring type magnetic head forsending and receiving signals with a magnetic medium, wherein initialpermeability μ₁ at rubbing direction and initial permeability μ₂ at gapdepth direction of the magnetic medium of substances comprising amagnetic circuit meet the following equation 17: ##EQU6## As a result, amagnetic head having excellent output characteristics can be obtained.

According to the sixth configuration of the magnetic head of thisinvention, the magnetic head comprises a ring type magnetic head forsending and receiving signals with a magnetic medium, wherein at leastferrite is used at one part of a composite material comprising amagnetic circuit of the magnetic head, and initial permeability μ₃ atrubbing direction and initial permeability μ₄ at gap depth direction ofthe magnetic medium of the ferrite meet the following equation 18:##EQU7## As a result, a magnetic head having excellent outputcharacteristics can be obtained.

According to the seventh configuration of the magnetic head of thisinvention, the magnetic head comprises a ring type magnetic head forsending and receiving signals with a magnetic medium, wherein at least amaterial composing the head is a bonded ferrite of a single crystalferrite and a polycrystal ferrite, and a rubbing side of the magneticmedium has initial permeability μ₅ at rubbing direction of the magneticmedium with the single crystal ferrite, and the part which does not rubwith the magnetic medium has initial permeability μ₆ magneticallyisotropic with the polycrystal ferrite, and permeabilities μ₅ and μ₆meet the following equation 19: ##EQU8## As a result, a magnetic headhaving excellent output characteristics can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing a first embodiment of a method foranalysis of magnetic recording characteristics of this invention.

FIG. 2 is a flow chart showing a second embodiment of a method foranalysis of magnetic recording characteristics of this invention.

FIG. 3 is a flow chart showing a third embodiment of a method foranalysis of magnetic recording characteristics of this invention.

FIG. 4 is a flow chart showing a fourth embodiment of a method foranalysis of magnetic recording characteristics of this invention.

FIG. 5 (a) to (c) are perspective views showing a conventional magnetichead.

FIG. 6 is a schematic view showing directions of magnetic moments withina magnetic head in the process of recording and reproducing in the firstembodiment of this invention.

FIG. 7 is a view showing an example of a split figure for a magneticdevice and a target area of analysis in the first embodiment of thisinvention.

FIG. 8 is a view showing stress σ_(x) at x direction of initialpermeability at x direction and dependency of stress σ_(y) at ydirection.

FIG. 9 is a perspective view showing a structure of a magnetic head inthe fourth embodiment of this invention.

FIG. 10 is a perspective view showing an example of a magnetic recordingand reproducing apparatus of this invention.

FIG. 11 is a graph showing the relationship between the anisotropy ofinitial permeability and the output of a magnetic head obtained in asixth embodiment of this invention.

FIG. 12 is a graph showing frequency dependency of initial permeabilityof a magnetic head obtained in the third embodiment of this invention.

FIG. 13 is a graph showing an example of frequency dependency of thereproduced output in a magnetic head obtained in the first embodiment ofthis invention.

FIG. 14 is a view showing the relationship between the magnetic momentand the magnetic field in the first embodiment of this invention.

FIG. 15 is a perspective view showing an example of a structure of amagnetic head in the sixth embodiment of this invention.

FIG. 16 is a perspective view showing an example of a structure of amagnetic head in a fifth embodiment of this invention.

FIG. 17 is a perspective view showing an another example of a structureof a magnetic head in the fifth embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention will be explained by referring to the followingillustrative examples and attached figures. The examples are notintended to limit the invention in any way.

First, an embodiment will be explained with the use of a magnetic headas one of typical magnetic devices.

In the manufacturing process of a magnetic head, it is often so that ananneal step of about 200° C.˜700° C. is included in order to removedistortions etc. caused while processing a magnetic substance.Furthermore, in the step of achieving bonding by using a non magneticmaterial 43 and the like such as glass etc. which is shown in FIG. 5 orin other steps, adhesion is accomplished by heating at the temperatureof about 400˜800° C. and pressurizing by an external force. Therefore,stress is given to the magnetic substance by thermal stress caused bythe difference of thermal expansion coefficients of the compositematerials or by external force, and a curve of magnetic flux.density--magnetic field strength changes through magnetostriction.Moreover, as shown in FIG. 5, since the magnetic head has a complicatedform, the distribution of stress becomes complicated as well. As aresult, the distribution of the curve of magnetic flux density--stressbecomes complicated. Accordingly, it is necessary to make a tremendouseffort for obtaining an optimum combination of initial permeability andform. It is effective to use an apparatus for analysis of magneticcharacteristics in order to obtain this optimum combination of initialpermeability and form, and also to obtain combinations of thermalexpansion coefficients between the magnetic substances 42, 44, 45 etc.and the non magnetic materials 41, 43, 46 etc.

EXAMPLE 1

FIG. 1 is a flow chart showing a first embodiment of a method foranalysis of magnetic recording characteristics of this invention. Anapparatus for analysis of magnetic characteristics comprises a datainput part 1, a coupled analysis part 2, and a result output part 3.

As shown in FIG. 1, the data input part 1 is provided with data relatedto the characteristics of substances composing a magnetic device, datarelated to the structure of the magnetic device, data concerning theboundary conditions for analysis of structure, and data concerning theboundary conditions for analysis of magnetic field (conditions formagnetic field supply). The characteristics of substances can be dividedinto mechanical characteristics and magnetic characteristics. Themechanical characteristics include a Young's modulus, a thermalexpansion coefficient, and a Poisson' ratio of each composite material.The magnetic characteristics include saturation magnetization, amagnetostriction constant, a domain wall mass, a damping-constant of adomain wall, recovering force of the domain wall, a gyro magneticconstant, a damping frequency of magnetization rotation, crystalmagnetic energy, a curve of magnetic flux density--magnetic fieldstrength at a specific azimuth, and initial permeability at a specificazimuth of each material, and at least one of these characteristics isinput. In addition, a curve of magnetic flux density--magnetic fieldstrength at a specific azimuth or initial permeability and the likeunder stressed condition may be input. The magnetic device and thetarget area for analysis are first divided into two areas and more, andthe form is input as nodal points and elements. The boundary conditionsfor analysis of structure comprise, for example, load received at eachelement or nodal point, stress, and stress caused by thermal distortion,and at least one of them is input. The boundary conditions for analysisof magnetic field are (1) to cause magnetic field through electriccurrent, and (2) to input a magnetic field, magnetization, or a magneticpotential directly. The split figures of the stress analysis part andthe matrix analysis part may be different. In that case, aninterpolation method can be applied to the distribution of the stressobtained from a stress analysis part 4 in order to obtain values of eachnodal point and each element in the matrix forming part 5. FIG. 7 showsan example of the split figure.

The coupled analysis part 2 consists of the stress analysis part 4, thematrix forming part 5, a solving part 6, and a convergence judgementpart 7. In the stress analysis part 4, analysis values of the stressdistribution are obtained with the use of a finite element method, aboundary element method, or a difference method etc. and based on thedata input from the date input part 1, with at least one boundarycondition selected from the group consisting of a thermal stressdistribution, an initial stress distribution, and load stress within themagnetic device, or the arithmetic sum of the aforementioned elements,or displacement of the magnetic device etc.

In the matrix forming part 5, one formula for obtaining the flow of themagnetic flux density of each element is solved, in combination with atleast one formula selected from the equations 1 to 4 for obtaining theflow of the magnetic flux density of the entire magnetic device. Bysolving the equations 1 to 4, the solution can be obtained, in whichenergy in the space where the magnetic device is present reaches theminimum. The equation 3 is a formula which shows the continuity ofmagnetic flux. The analysis of magnetic characteristics in the magneticdevice can be conducted by constructing formulas for each element byusing at least one method selected from the group consisting of amagnetoresistive method, a finite element method, a boundary elementmethod, a finite difference method, a boundary integral method, anintegral equation method, a surface charge method, a charge simulationmethod, and a magnetic moment method.

In the high frequency area of over 1 MHz, magnetic phenomena can beexplained by the dynamic movement of an electron spin. The flow ofmagnetic flux within a magnetic body can be explained mainly bymagnetization rotation. Frequency dependency of a magnetic moment at thetime when the movement of the spin conducting precession is obstructedby a relaxation mechanism is know as Landau-Lifshitz equation and isshown as the equation 6 (Reference: Physics of Ferromagnetic Body,Author: Soushin Chikakado, Publisher: Shoukabou, 1984). ##EQU9## In theabove-noted equation, θ represents a direction of the spin shown in FIG.14, γ represents a gyro magnetic constant, μ₀ =4πX 10⁻⁷. λ represents adamping frequency, and t represents time. The internal energy E is shownin the equation 7 as the sum of crystal magnetic energy,magnetostriction energy, and energy by the effective magnetic fieldH_(eff). ##EQU10## In the above-noted equation, K₁ represents crystalmagnetic energy, H_(eff) represents a sum of an external magnetic fieldH ₀ and a demagnetization field H_(d). λ₁₀₀ represents amagnetostriction constant at (100) direction, λ₁₁₁ represents a magneticconstant at (111) direction, σ represents stress at i direction, I_(s)represents saturation magnetization, i represents x, y, and z, α_(j)represents a direction cosine formed between the magnetic field with theazimuth shown in FIG. 14 and the crystal orientation, and γ_(ji)represents a direction cosine of stress at i direction.

By solving the equation 6, the magnetization mode within the magneticbody can be described. For example, when art external magnetic field isdetermined as an alternating current magnetic field shown as H₀ =H₁e^(j)ωt, magnetic fluxφ (ω) within a microelement can be described asthe equation 8. ##EQU11## In the above-noted equation, H₁ represents astrength of the magnetic field of external alternating current, jrepresents an imaginary number, ω represents an angular velocitycalculated by 4πx frequency, and ω₀ represents a value shown as theequation 9. ##EQU12##

For obtaining a magnetic flux density of each element, a domain wallmotion may be added to the equation 6. For example, the equation ofmotion with 180 degrees domain wall is shown as the equation 10(Reference: Physics of Ferromagnetic Body, Author: Soushin Chikakado,Publisher: Shoukabou, 1984). ##EQU13## In the above-noted equation, mrepresents a mass of a domain wall per unit area, β₁₈₀ represents adamping coefficient of the domain wall, s represents energy of thedomain wall, and α represents a recovering force of the domain wall.

A formula for obtaining the flow of magnetic density in the entiremagnetic device can be described by using the finite element method, inwhich B is a magnetic flux density and A, a magnetic vector potentialdefined as the equation 11, is determined as an unknown quantity.

    B=rot A                                                    (equation 11)

The finite element method is used for solving, so that the formula of amagnetic field obtained by substituting the equation 11 with theMaxwell's equations also holds good for the entire magnetic device.Furthermore, the magnetic vector potential was used as an unknownquantity in this embodiment, but it is also possible to use unknownvariables, for example, a magnetic vector potential and an electricscalar potential, a magnetic scalar potential, a magnetic scalarpotential and an electric vector potential, a magnetic field strengthand a magnetic scalar potential, a magnetic vector potential and anelectric scalar potential and a magnetic scalar potential, a magneticvector potential and a magnetic scalar potential, a field strength and amagnetic scalar potential, a magnetic field strength, a magnetic fluxdensity etc. Besides the finite element method, by using at least onemethod selected from the group consisting of a magnetoresistive method,a boundary element method, a finite difference method, a boundaryintegral method, an integral equation method, a surface charge method, acharge simulation method, a magnetic moment method and the like, theformula of a magnetic field can be solved as formula of each element.

By solving the equations simultaneously in combination, instability ofthe solution caused by having a non-linear part or divergence of thesolution can be avoided, so that the convergence solution can beobtained stably. As for each element k, when it is A_(k) (θ_(k),H_(k))=0 in the equations 1 to 4 and when the solutions of the equations6 and 10 are shown as φ_(k) (θ_(k), H_(k))=0, θ_(k), H_(k) which satisfythe both can be obtained in the following equation. ##EQU14##

The solving part 6 is a part, where a group of equations combined byGauss elimination and an ICCG method etc. is solved, and the convergencecondition of the solution is judged in the convergence judgement part 7,and when convergence took place, the solution is then output at theresult output part 3. Recording characteristics of the magnetic head canbe obtained by providing electric current into a coil 64 of FIG. 6 whichforms an interlinkage with a part 52 of a magnetic head 61, and bycalculating leakage flux occurring from a magnetic gap 41. Furthermore,reproducing characteristics of the magnetic head can be obtained bydisposing a magnet to a magnetic tape 62 disposed on top of the magneticgap 41, and by calculating the amount of magnetic flux at the magneticflux moment 52 which flows inside the magnetic head 61 caused by thegenerated magnetic field. In addition, by the movement of the magnet,the amount of electric current induced in the coil 64 may be calculatedas well.

The result output part 3 is a part where the data obtained by thecoupled analysis part 2, for example, a distribution of magnetic fluxdensity, a distribution of magnetic moment, a graph showing lines ofmagnetic flux, an equipotential line, a distribution of magnetic fieldstrength, and recording characteristics and reproducing characteristicsin the magnetic head are output, and this part comprises a printer, acathode ray tube (CRT), a plotter and the like.

An example of frequency dependency of the reproducing output of themagnetic head obtained in the above-mentioned way is shown in FIG. 13.It is preferable that the reproducing characteristics of the magnetichead show a high absolute output value and extend up to a high outputfrequency.

EXAMPLE 2

FIG. 2 is a flow chart showing a second embodiment of a method foranalysis of magnetic recording characteristics of this invention. Anapparatus for analysis of magnetic recoding characteristics of thisinvention comprises a data input part 1, a serial analysis part 10 whichconducts the analysis of the flow of magnetic flux density in eachelement and the analysis of magnetic characteristics in the entiremagnetic device alternately, and a result output part 3.

As shown in FIG. 2, various data are input to the data input part 1, asin the first embodiment.

The serial analysis part 10 comprises a stress analysis part 4, aninitial value input part 14, a magnetic flux density calculating part11, a matrix forming part 12, a solving part 13, and a convergencejudgement part 7. First, in the stress analysis part 4, a stressdistribution within the magnetic device is obtained based on the datainput from the data input part 1, as in the first embodiment. In theinitial value input part 14, an initial value of the effective magneticfield H_(eff) is determined. Then, in the magnetic flux densitycalculating part 11, a magnetic field dependent curve of magnetic fluxdensity for each element can be calculated by using the equations 6 and10. Next, in the matrix forming part 12, magnetic characteristics of theentire magnetic device are described with the equations 1 to 4, andformulas for each element are formed by means of a method selected fromthe group consisting of a magnetoresistive method, a finite elementmethod, a boundary element method, a finite difference method, aboundary integral method, an integral equation method, a surface chargemethod, a charge simulation method, a magnetic moment method.Thereafter, in the solving part 13, a magnetic flux density and amagnetic field distribution of each element can be obtained. By usingthe magnetic field distribution obtained in this way, the magnetic fluxdensity of each element is obtained in a magnetic flux densitycalculating part 11, and the magnetic characteristics of the wholemagnetic device are obtained in the matrix forming part 12. Theconvergence conditions of the solutions obtained by alternatelycalculating in the magnetic flux density calculating part 11 and in thematrix forming part 12 are judged, and when convergence took place, theconvergence solutions are forwarded to the result output part 3.

In order to conduct a three-dimensional analysis of magnetic solutions,the number of elements will be extremely large, so that a large-scalecalculation will be necessary. When the calculation formulas of themagnetic flux density and the Maxwell's equations for the entiremagnetic device are solved separately, the scale of the matrix can bereduced. In this way, the present calculators can be used effectively,and it is therefore possible to calculate in a practical time.

EXAMPLE 3

FIG. 3 is a flow chart showing a third embodiment of a method foranalysis of magnetic recording characteristics of this invention. Anapparatus for analysis of magnetic recording characteristics of thisinvention comprises a data input part 1, a coupled analysis part 22which conducts the analysis for obtaining the initial permeability ofeach element and the analysis of magnetic characteristics in the entiremagnetic device in combination, and a result output part 3.

As shown in FIG. 3, various data are input to the data input part 1, asin the first embodiment.

The coupled analysis part 22 comprises a stress analysis part 4, amatrix forming part 25, a solving part 6, and a convergence judgementpart 7. First, in the stress analysis part 4, stress within each elementis obtained based on the boundary conditions input from the data inputpart 1, and at the same time, the initial permeability of each elementis obtained from at least one of the equations 6 or 10, and and thencombined with Maxwell's equations for the entire magnetic device. Then,solutions are obtained in the solving part 6, which are forwarded to theresult output part 3.

Assumed that the form is flat and the magnetization rotates within theplane as with a magnetic head, and when the equation 6 is solved underthis assumption, the initial permeability due to a rotationalmagnetization can be shown as the equation 13 below. ##EQU15## In theabove-noted equation, β_(rot) represents a damping constant of arotational magnetization.

Furthermore, by solving the equation 10, the initial permeability due toa domain wall motion can be shown as the equation 14. ##EQU16## In theabove-noted equation, σ represents stress at a principal axis direction,n represents a number of domain walls contained per unit volume, andinitial permeability μ of the system is shown as the equation 15.

    μ(ω)=μ.sub.rot +μ.sub.180                   (equation 15)

FIG. 8 shows the stress σ_(x) at x direction of the initial permeabilityat the x direction and the dependency of stress σ_(y) at y directionobtained in the above-noted way with 10 MHz. An example of calculatingfrequency dependency of the initial permeability is shown in FIG. 12. InFIG. 12, a mark ∘ indicates whole initial permeability μ, a mark ♦indicates initial permeability μ_(rot) due to rotational magnetization,and a mark ▴ indicates initial permeability μ₁₈₀ due to a domain wallmotion.

For example, the initial permeability can be described with a rotationalmagnetization moment only in a sufficiently low frequency area, and whenthe sliding direction is determined as (110) plane and the gap depthdireciton as (100) plane, the equation 15 can be described in thesimplified formula as shown below. ##EQU17## In the above-notedequation, K₁ and K₂ represent crystal magnetic energy, σ_(x), σ_(y), andσ_(z) respectively represents stress at sliding direction, stress atwidth direction, and stress at gap depth direction.

EXAMPLE 4

FIG. 4 is a flow chart showing a fourth embodiment of a method foranalysis of magnetic recording characteristics of this invention. Anapparatus for analysis of magnetic recording characteristics of thisinvention comprises a data input part 1, a serial analysis part 30 whichalternately conducts calculation of initial permeability of each elementand formation of matrix for the entire magnetic device, and a resultoutput part 3.

As shown in FIG. 4, various data are input to the data input part 1, asin the first embodiment.

The serial analysis part 30 comprises a stress analysis part 4, aninitial value input part 14, initial permeability calculating part 31, amatrix forming part 32, a solving part 13, and a convergence judgementpart 7. First, in the stress analysis part 4, a stress distributionwithin the magnetic device is obtained based on the boundary conditionsinput from the data input part 1. Next, in the initial value input part14, an initial value of the effective magnetic field H_(eff) isdetermined. Then, in the initial permeability calculating part 31,initial permeability of each element can be calculated by using theequations 13 and 15. Next, in the matrix forming part 32, magneticcharacteristics of the entire magnetic device are described with theequations 1 to 4. Thereafter, by solving formulas for each element inthe solving part 13 by means of at least one method selected from thegroup consisting of a magnetoresistive method, a finite element method,a boundary element method, a finite difference method, a boundaryintegral method, an integral equation method, a surface charge method, acharge simulation method, a magnetic moment method, a magnetic fielddistribution of each element can be obtained. By using the magneticfield distribution of solutions obtained in the above-noted way, themagnetic flux density of each element is obtained in initialpermeability calculating part 31, and the magnetic characteristics forthe whole magnetic device are obtained in the matrix forming part 12.The convergence conditions of the solutions obtained by alternatelycalculating in the initial permeability calculating part 31 and in thematrix forming part 12 are judged, and when convergence took place, theconvergence solutions are forwarded to the result output part 3.

In the above-mentioned embodiment, the initial permeability or the curveof magnetic flux density--magnetic field was obtained by using theequation 6 and the equation 10, but it is not limited to this methodonly. For example, it is also possible to obtain the initialpermeability or the curve of magnetic flux density--magnetic field byusing an anticipated theoretical value and an experimental value and byconducting compensation with spline compensation and the like.Furthermore, these results can be formed as a table for reference. Also,a neuro-processing having learning function or a fuzzy calculation isalso effective for obtaining the relationship between the stress and theinitial permeability and the relationship between the stress and thecurve of magnetic flux density--magnetic field.

As described above, magnetic characteristics of a magnetic head materialchange according to thermal stress and external force. Therefore, it isextremely effective from the viewpoint of designing a magnetic head toobtain the curve of magnetic flux density--magnetic field strength orthe distribution of the initial permeability from stress distributionand to form such that each part has a higher curve of magnetic fluxdensity--magnetic field strength than in the time of no stress. In thiscase, the high curve of magnetic flux density magnetic field strengthmeans that higher magnetic flux density is possessed with lower magneticfield strength.

As shown in FIG. 9, the whole structure can be simplified and consideredseparately as a part 75 where a magnetic moment is oriented to thesliding direction and as a part 76 where a magnetic moment is orientedto the gap depth direction. In the magnetic head, by separately takingthe curve of magnetic flux density--magnetic field strength at slidingdirection of the tape of the material comprising the magnetic circuitand the curve of magnetic flux density--magnetic field strength at thegap depth direction into consideration, when the stress due to thermalstress and external stress is optimized, the curve of magnetic fluxdensity--magnetic field strength can be formed higher than in the timeof no stress both at sliding direction and at gap depth direction.

EXAMPLE 5

It is effective for the improvement of magnetic recording efficiency toimpose stress on materials comprising a magnetic circuit by bondingsubstances having different thermal expansion coefficient with thematerial composing the head to one side or both sides of a ring typemagnetic head, and to make the initial permeability to be higher thanwith the state without stress.

FIG. 16 is a perspective view showing an embodiment of a magnetic headof this invention. As shown in FIG. 16, glass 122, 123 having a lowerthermal expansion coefficient than ferrite are attached on the sidesurfaces of a ferrite head 121 having a negative magnetostrictionconstant. It is configured such that tensile stress 121 is imposed onthe ferrite to enhance the initial permeability of the side surface atgap depth direction to be higher than the initial permeability in thetime of no stress. Substances attached on the side surfaces of theferrite head are not limited to glass. It is also possible to useceramics and plastics etc. besides glass. Furthermore, it goes withoutsaying that other magnetic materials besides ferrite such as a metalmagnetic film can be used as well.

When the magnetostriciton constant of a magnetic material such asferrite should be positive, the initial permeability of the side surfaceat gap depth direction can be enhanced to be higher than that in thetime of no stress by using materials having larger thermal expansioncoefficient than the magnetic material.

As shown in FIG. 16, non magnetic materials such as glass 122, 123 maybe disposed on both sides or only on one side of a ring type magnetichead (ferrite head 121). Furthermore, as shown in FIG. 17, the nonmagnetic materials 132 such as glass may be disposed on the back sidesof a ring type magnetic head 131. As for the combination and the form ofthese magnetic and non magnetic materials, it is effective to select thematerials and to design the form most suitably with the use of theabove-mentioned apparatus for analysis of magnetic recordingcharacteristics 131.

EXAMPLE 6

The above-noted method of analysis is also applicable when thedifference of thermal expansion coefficient and external force etc. ofthe material are small so there is almost no stress.

FIG. 11 shows the results of conducting an analysis of the recording andreproducing characteristics by using initial permeability μ₁ at rubbingdirection 75 and initial permeability μ₂ at gap depth direction 76 shownin FIG. 9. As shown in FIG. 11, in a ring type magnetic head 71 whichsends and receives signals with a magnetic medium, and when thepermeability at the tape rubbing direction 75 of a magnetic material 63comprising the magnetic circuit is determined as μ₁ and the permeabilityat gap depth direction 76 is determined as μ₂ then, it becomes clearthat the output characteristics are satisfactory in the area where μ₁/μ₂ corresponds to the equation 17. ##EQU18##

As shown in FIG. 15, a bulk type magnetic head 111 is manufactured byusing a single crystal ferrite, and when the permeability at rubbingside direction 115 is determined as μ₃ and the permeability at gap depthdirection 116 is determined as μ₄, then, it becomes clear that it issatisfactory in the area where μ₃ /μ₄ corresponds to the equation 18.##EQU19##

A bulk type magnetic head was manufactured by using a single crystalMn-Zn ferrite having anisotropy in the initial permeability (Fe₂ O₃=54%, MnO=27%, ZnO=19%, initial permeability at (100) direction=500,initial permeability at (110) direction =400). In other words, by usingthis single crystal Mn-Zn ferrite, a magnetic head having the (100) axisdirection in the rubbing direction 75 and the (110) axis direction inthe gap depth direction 76 was manufactured as shown in FIG. 9.Therefore, in this embodiment, μ₁ was 500 and μ₂ was 400. As aComparative Example 1, a magnetic head having the (110) axis directionin the rubbing direction and the (100) axis direction at gap depthdirection was manufactured. In the Comparative Example 1, μ₁ was 400 andμ₂ was 500. Furthermore, as a Comparative Example 2, a magnetic headusing a polycrystal ferrite having the permeability of 450 wasmanufactured. In the Comparative Example 2, μ₁ was 450 and μ₂ was 450.These magnetic heads were installed in a video tape recorder of VHSsystem having the structure shown in FIG. 10, and the recording andreproducing characteristics were compared. As shown in FIG. 10, the VTRapparatus functions such that a magnetic head 81 is mounted to amagnetic head mounting window 82 disposed on a rotating drum 83, and amagnetic tape 62 is wound helically around a fixed drum 84 and arotating drum 83. The signals which are input via a reproducingamplifier 87 and recorded by a magnetic head 81 are once again read outat the magnetic head 81, and the signals are output after amplifying thesignals with the reproducing amplifier 87. When the above-mentionedrecording and reproducing characteristics of the magnetic heads werecompared by the relative amounts, this embodiment shown in FIG. 9 had+1dB, the Comparative Example 1 had -0.2dB, and the Comparative Example2 had +0.3 dB. Therefore, in a ring type magnetic head which sends andreceives signals with a magnetic medium, it is effective to design suchthat the permeability at the tape rubbing direction of a materialcomprising the magnetic circuit becomes higher than the permeability atgap depth direction.

Moreover, this embodiment shown in FIG. 15 had μ₃ /μ₄ =1.25, whereas theComparative Example 1 had μ₃ /μ₄ =0.8 and the Comparative Example 2 wasμ₃ /μ₄ =1.0. As a result, the calculation results proved that thisembodiment had higher output characteristics than that of theComparative Examples 1 and 2.

Furthermore, in a ring type magnetic head 111 which sends and receivessignals with a magnetic medium as shown in FIG. 15, at least thematerial composing the head comprises a bonded ferrite bonding a singlecrystal ferrite 113 and a polycrystal ferrite 112, and when the taperubbing surface has the permeability μ₅ at tape rubbing direction 115with the single crystal ferrite 113 and has the magnetically isotropicpermeability μ₆ with the polycrystal ferrite 112, it becomes clear thatthe magnetic head is constructed to fulfill the following equation:##EQU20## In this embodiment, it was explained by referring to the bulktype magnetic head 38 shown in FIG. 5 (a), but it goes without sayingthat the same effects can be attained by using a metal-in-gap typemagnetic head 39 shown in FIG. 5 (b), and a laminate type magnetic head40 shown in FIG. 5 (b).

EXAMPLE 7

FIG. 10 is a schematic view showing an example of a magnetic recordingand reproducing apparatus of this invention. shows a tenth embodiment ofthis invention. In FIG. 10, 81 represents a magnetic head optimized bythe above-mentioned analysis apparatus of magnetic characteristics ofthis invention, 82 represents a magnetic head mounting window, 83represents a rotating drum 83, 84 represents a fixed drum, 62 representsa magnetic tape, and 86 represents a tape running direction. Theabove-mentioned ring type magnetic head having different permeabilitiesat tape rubbing direction and at gap depth direction in FIG. 10 isinstalled to the head mounting window 82 disposed on the rotating drum83. The magnetic recording and reproducing are conducted by the relativemovement of the magnetic head 81 and the magnetic tape 62. In this way,a magnetic recording apparatus having high recording and reproducingcharacteristics can be obtained. Although this embodiment referred to anupper drum rotating system such as VTR of VHS system, 8 mm VTR system,and DAT, it goes without saying that this invention can be also used forthe D2 system etc. having a middle drum rotating system, an audiocassette recorder having a fixed pass system, or for magnetic heads suchas a hard disc and a floppy disc. By using a magnetic head optimized bythe above-noted apparatus for analysis of magnetic recordingcharacteristics, it is considered as being possible to greatly improvethe characteristics of the magnetic recording and reproducing apparatus.

The magnetic recording apparatus referred to in this embodiment can beused also as a recording apparatus for a photomagnetic apparatus using amagnetic head in the recording or in the reproducing process.

In this embodiment, it was explained by referring to a bulk typemagnetic head, but it goes without saying that the same effects can beattained by using a metal in gap type magnetic head and a laminate typemagnetic head. Also, it was explained by referring to a ring typemagnetic head, but the above-mentioned apparatus for analysis ofmagnetic recording chararcteristics is also applicable for a non-ringtype magnetic head such as a single magnetic pole head used for verticalrecording. It is obvious that the method of this invention is effectivefor optimizing magnetic characteristics of a magnetic device such as atransformer or a LCR circuit.

The analysis part of magnetic characteristics of this invention may beattained from the viewpoint of software or of firmware by using acomputer.

In addition, it is also effective to neuro-process the output resultsand by learning to optimize the size, form, structure, thermodynamics ofthe composite material, magnetic characteristics such asmagnetostriction, and the like.

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof. The embodiments disclosedin this application are to be considered in all respects as illustrativeand not as restrictive. The scope of the invention is indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

What is claimed is:
 1. A magnetic head comprising a ring type magnetichead for sending and receiving signals with a magnetic medium,whereinthe material comprising said ring type magnetic head includes at leastferrite, said ferrite having a negative magnetostriction constant, and amaterial having a smaller thermal expansion coefficient than that ofsaid ferrite is attached on the side surface of said ring type magnetichead in a magnetic path on the side of the head being formed in gapdepth direction, wherein a curve of magnetic flux density versusmagnetic field strength in rubbing direction differs from a curve ofmagnetic flux density versus magnetic field strength in gap direction ofsaid magnetic medium of substances comprising a magnetic circuit, andeach substance has a higher curve of magnetic flux density versusmagnetic field strength than at a time of no stress on said ring typemagnetic head, and wherein initial permeability μ1 in rubbing directionand initial permeability μ2 in gap depth direction of said magneticmedium of substances comprising a magnetic circuit meet the followingformula 1:

    1.1<μ1/μ2<1.4                                        (formula 1).


2. A magnetic head comprising a ring type magnetic head for sending andreceiving signals with a magnetic medium,wherein the material comprisingsaid ring type magnetic head includes at least ferrite, said ferritehaving a negative magnetostriction constant, and a material having asmaller thermal expansion coefficient than that of said ferrite isdisposed on the back side of said ring type magnetic head a magneticpath on the side of the head being formed in gap depth direction,wherein a curve of magnetic flux density versus magnetic field strengthin rubbing direction differs from a curve of magnetic flux densityversus magnetic field strength in gap direction of said magnetic mediumof substances comprising a magnetic circuit, and each substance has ahigher curve of magnetic flux density versus magnetic field strengththan at a time of no stress on said ring type magnetic head and whereininitial permeability μ3 in rubbing direction and initial permeability μ4in zap depth direction of said magnetic medium of substances comprisinga magnetic circuit meet the following formula 2:

    1.1<μ3/μ4<1.4                                        (formula 2).